1. Field of Invention
The current invention relates generally to apparatus, systems and methods for detecting radar. More particularly, the apparatus, systems and methods relate to detecting low power spread spectrum radars. Specifically, the apparatus, systems and methods provide for detecting low power spread spectrum radars by analysing the same signal received by two orthogonal radio frequency inputs.
2. Description of Related Art
Modern spread spectrum radars are significantly more difficult to detect and characterize than the conventional Radar. One reason for this is because the transmit power is reduced from typically 4000 watts to under 100 watts. In addition to reduced transmit power, these radars use modulation waveforms that spread the RF energy over a broad spectrum. The combination of reduced transmit power and spread spectrum make these radars extremely difficult to detect. Significant additional processing gain over state of the art radar waming receivers may be needed. In addition to detection, signal parameter estimation may be especially challenging. Some radar detectors support coarse frequency and time of arrival (TOA) measurements based on the channelizer bin detection and the filtered pulse envelope. However to detect spread spectrum radars accurately, more resolution on both of these measurements is needed.
Other conventional techniques extract the phase time history of the signal and fit a straight line to the phase data. The slope of the phase line is the frequency. Various algorithms approach the Cramer Rao Lower Bound at signal to noise ratios higher than 6 dB. However, modern radars may need to look at a range of SNRs from −5 dB to +10 dB. A need, therefore, exists for a better radar (unknown signal) detector.